Drafting instrument



April l2 1938 R. M. LINDSAY 2,114,081

DRAFTING INSTRUMENT April 12, 1938. R. M. LINDSAY 2,114,081

DRAFTING' INSTRUMENT Filed April 50, 1936 2 Sheets-Shee'. 2

@a Jar I Patented Apr. 12, 1938 UNTTED STATES 2,ll4,i

DRAFTING INSTRUMENT Robert M. Lindsay, Oak Park, Ill., assignor to Metal Specialties Manufacturing Co., Chicago, Ill., a corporation of Illinois Application April 30, 1936, Serial No. 77,283

3 Claims.

This invention relates particularly to a parallel-movement drafting instrument adapted to be used on a drafting-board in lieu of a T-square.

The primary object is to provide a simple instrument of the character indicated, which is of universal adaptability, in the sense that the pneumatic holder with which the instrument is equipped is adapted to hold securely any simple ruling-device, such as a triangle, a French curve, a ruler, or any other similar device which presents an edge which will enable curves, whether straight or of other shape, to be drawn.

The invention is illustrated in a preferred embodiment in the accompanying drawings, in which- Fig. 1 is a plan view of a drafting board with the improved drafting instrument applied thereto, the full lines indicating one position of the drafting instrument and the dotted lines indicating another position; Fig. 2, an enlarged broken sectional View taken as indicated in line 2 of Fig. 1, showing the manner in which the pneumatic-holder is secured to the parallel-movement head employed; Fig. 3, an enlarged broken sectional view taken as indicated at line 3 of Fig. 1; Fig. 4,. a broken plan View showing the clamping nut removed from the threaded stud with which the pneumatic-holder is equipped, thus exposing the graduations for angular adjustment of the pneumatic-holder with respect to the parallelmovement head; and Fig. 5, a broken sectional View taken as indicated at line 5 of Fig. 4.

In the illustration given, A designates a drafting-board having a sheet A of drafting paper mounted thereon; B, an adapter secured to one corner portion of the board, said adapter preferably comprising an attaching clip B and a link-connecting clip B2 detachably held by the clip B; C, a parallel-movement head; D, a pneumatic-holder adjustably secured pivotally to the head C, for angular adjustment; E, a rulingdevice, shown as atriangle, gripped by the pneumatic-holder; and F, jointed parallel-link mechanism connecting the clip B2 and the head C.

The drafting-board C may be of any suitable construction.

The member B of the adapter is shown as comprising a sheet metal member l which is secured to an edge of the drafting-board, as by screws l a. The member l has a pair of resilient arms lb formed integrally with the member l and projecting o-ver the upper surface of the board A.

The member B2 of the adapter is shown as a sheet metal clip which is provided with an intermediate elevated link-bearing portion 2, supported by upright portions 2a, and depressed endportions 2b adapted to be clamped between the spring-arms lbandtheupper surface of the drafting-board. The extremities 2b of the adapterm-ember B2 preferably are provided with perforations 3 which receive depressed lugs d with which the arms Ib are provided. The extremities of the arms are curved upwardly as indicated at le. These extremities serve as finger pieces, by means of which the arms may be lifted to enable the member B2 to be withdrawn.

The head C is shown as a yoke-like sheet metal plate having a pivot-portion '5 and a segmental portion 5a to which the link-mechanism is attached. The pivot-portion E is preferably depressed below the plane of the segmental portion 5a, as will be understood from Fig. 2. The pivot-portion 5 preferably is provided on its upper surface with radial graduations associated with degree-marldngs designated, generally, by the numeral 6. Any suitable degree-graduations may be employed. Preferably, a zero graduation appears at each end of a transverse line across the pivot-portion of the head, and the quarters making up the extremity of the pivot-portion are graduated in reverse directions from Zero to 90.

The pneumatic-holder D preferably comprises a sheet-metal bar, or cross-head, 1, from the end-portions of which depend suction-cups la. The upper side of the member l is provided along the longitudinal center of the member with marks disposed at opposite sides of the pivotportion 5 of the head C. The member 'l is provided at its central portion with an upwardly projecting xedly secured threaded stud ii which extends through a pivot-perforation in the member 5 and is equipped above the member 5 with a clamping-nut ii).

The suction-cups 'la are adapted to be pressed downwardly upon a plane surface with which the ruling-member is provided and caused to suctionally grip the ruling-member. The rulingmember may be of any suitable form. It may, for example, be a Celluloid triangle. It has been found in practice that the holder D may be reliably secured tc the member E, or any other desirable form of ruling-member, by the suctioncups employed.

As shown in Fig. 5, the suction-cup is composed of rubber having imbedded in its crown-portion the base of a short threaded stud ll which extends through a perforation in the end-portion of the member 1 and is securely fastened by means of a nut I la. A plurality of the suction-cups preferably is employed. As illustrated, the member l is equipped at each end with a suction-cup.

The height of the segmental portion 52 of the head C preferably corresponds approximately with the height of the raised central portion 2 of the link-attaching clip B2.

The parallel link-mechanism F comprises, in addition to the adapter-clip B2 and they segmental portion 5a of the head C, two pairs of parallel links I2 and I3 which are jointedly connected together by means of a joint-plate I4, shown as a ring punched from sheet metal. The initial pair of links I2 are connected With the clip B2 by pivot-rivets I5 and I6. The other ends of the links I2 are connected with the joint-disk I4 by pivot-rivets I'I and I8.

The links I3 are connected with the head C by pivot-rivets I9 and 20. At their other ends, the links I3 are connected with the joint-ring I4 by pivotal connections 2| and 22. The links I2 are shown as extending below the plane of the ring I4, and the links I3 are shown as extending above the plane of the ring I4.

The bearings for the links I2 and I3 afforded by the elevated clip 2 and the segmental portion 584 of the head C are suiliciently extended to support the link mechanism well above the plane of the drafting board. As appears from Fig. 2, the cross-head D is adapted to swing in a plane beneath the head C to any desired position of angular adjustment.

In adapting the implement to the drafting board, a straight edge of the ruling device E may be placed parallel with an edge of the draftingboard. The pneumatic-holder D may be set at the zero mark and firmly clamped to the head C, and the pneumatic holder may then be pressed down firmly upon the member E. This establishes the straight edge in parallel relation with the edge of the drafting-board. The draftinginstrument may then be manipulated to bring the ruling-device E to any desired position, and the parallel movement will be maintained.

It is possible now to loosen the clamping nut I0 and turn the pneumatic-holder D to any desired position of angular adjustment. Then, by clamping the parts together, the desired angle of the straight edge is assured. The triangle E may now be moved to any desired position over the paper, and will always maintain the angle to which it has been set. Cross-hatching or ruling at any desired angle may be readily accomplished.

Obviously, the improved drafting implement is adapted to suctionally grip any ruling device which is provided with a suitable surface to make air-tight contact with the peripheral edges of the suction-cups. French curves, rulers of any desired shape, etc.. may therefore be used in lieu of the triangle E, the improved drafting implement being thus universal in its application.

Heretofore, drafting machines employing parallel link mechanisms have been extensively used. However, such instruments have ordinarily been very expensive, the price being prohibitive for classroom purposes, or for popular purposes, generally. In such devices, rulers, or other rulingdevices, ordinarily are connected with the holder by dovetail connections, Which are not only expensive but also do not lend themselves to universality.

The improved device may be manufactured so cheaply that it can be sold at a popular price, say at a retail price of $1.00 to $1.50. The improved drafting instrument is rather universal in its application to various forms of ruling devices, and may be reliably used. Its cost is only a fraction of the cost of drafting machines now on the market for similar use.

If desired, the adapter-member B may be omitted. In such case, the adapter-member B2 may be secured directly to the upper surface of the drafting-board by means of screws passing through the perforations 3. Thus, the member B2 would become a single-member adapter.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible in view of the prior art.

What I claim as new and desire to secure by Letters Patent is:

l. A drafting instrument comprising: an adapter having means for attachment to a drafting board; a parallel-movement head; two pairs of parallel links and an interposed joint-plate connecting said pairs, one of said pairs being connected to said adapter and the other pair being connected to said head, whereby said head will be constrained for parallel-movement; said adapter comprising a clip provided with means for attachment to the drafting board, and a coacting detachable bearing plate having pivotal connections with the initial ends of the initial pair of links; and a holder pivotally secured to said head and equipped with means for attaching a ruling-implement thereto.

2. A drafting instrument comprising: an adapter having means for attachment to a drafting board; a parallel-movement head; two pairs of parallel links and an interposed joint-plate connecting said pairs, one of said pairs being connected to said adapter and the other pair being connected to said head, whereby said head will be constrained for parallel movement; said adapter comprising a clip having means for attachrnent to a drafting board and having spaced resilient arms projecting over the board, and a link-connecting clip detachably held by said arms and having an elevated link bearing portion pivotally connected with the initial ends of the initial pair of links; and a pneumatic holder adjustably secured to said head and equipped with suction means for releasably attaching a rulingimplement thereto.

3. In combination: an adapter provided with means for attachment to a drawing board; a parallel-movement head linked to said adapter, said head having an elevated portion connected with the parallel-movement links and having a depressed pivotal portion tc which said holder is secured for angular adjustment; and a pivotallysecured, angularly adjustable holder beneath and carried by said head, said holder being provided with means for securing an underlying rulingimplement thereto.

ROBERT M. LINDSAY. 

